Well... they may be all random orbital, actually they are Dual-Action, Random Orbital + Rotation, but there are major differences between the models.
In the case of Griot's Garage machines, they offer the normal DA which is called the 6 inch machine I think. The difference between that and your PC is the power of the motor. So it's a little bit better than the PC. Both are 8mm throw machines, meaning the orbit of the pad is 8mm wide.
Then you have the Boss serie which has 2 machines: The G15 and the G21. The number represents the throw, so a 15mm machine and a 21mm one. The larger the throw, the more correction capability the machine has, so at the same motor power, a 21mm will correct paint faster than a 15mm and way faster than an 8mm. The downside to larger throw is that they don't work well on curved panels, especially if it's a concave panel. If find that the sweet spot is with the 15mm machine, but a 21mm with a 5 inch backplate will work nicelly in most cases.
Forced rotation are different beasts, I have never used one but think of them as a rotary polisher that has a bit of orbital action. I know they are harder to control and that they vibrate more, and for those two reasons I have never been interested in one but there are plenty of detailers who swear by them. Again, those are gonna offer much better correction than you PC.